VP engine knocks on cold start

[muggie]

Has anyone had any problems with engine knock on cold start?
Have spent heaps on new lifters, cam, timing chain etc.

It only knocks first in the morning, have had oil pressure tested that many times and all ok.
The oil and filter changed every 5,000 ks or sooner some times.

It has 195,300 on the clock, can not afford new motor.
Any help would be appreciated.

muggie

[greenfoam]

My V6 gives some rattles on the first start of the day, especailly if it hasn't been started for a few days, it's just old age don't worry about it . I've heard a mint gen III SS do a warm start next to me at the petrol station one day and it was slapping heaps more than my V6 on a cold start

[muggie]

My V6 gives some rattles on the first start of the day, especailly if it hasn't been started for a few days, it's just old age don't worry about it . I've heard a mint gen III SS do a warm start next to me at the petrol station one day and it was slapping heaps more than my V6 on a cold start

Thanks Greenfoam, do you still have any chips left for vp 3800???

[LowVp]

almost all of them will do it that have a few k's on them yeah nothing to worry about just mains making there noise saying they want oil

[s_pack]

Be wary about this, my VN started foing this about 8 months ago, just a really slight knock after startup in the morning. It slowly started to knock longer, louder, more often untill it started knocking slightly while driving. Two weeks ago, this engine was undrivable, just a constant knocking almost slapping noise that you could hear from miles away.

I didn't think anything of the problem untill a couple of months after it started, having not really noticed it that much. Anyways, i came to the conclusion that it was either piston slap, or a futher down problem, big end bearings or something, either way, it wasn't what i needed.

[CSL]

s_pack cracked flywheel mabye??

[G3MINI]

I've got a VN V6 in my gemini and no idea how many kms on the engine but over the last 4 years that i've owned it, it has always had a knock on the first start of the day. I was told it was just that the oil is still sitting in the sump and not lubricating the engine yet. It hasnt changed over the last 4 years so i havnt worried about it to much. It also has a tick in the top end of the engine I assume are worn lifters. Once again no change in 4 years so i guess its just the commo engine showing age. Still a reliable engine though i think.

[samuels]

Has anyone had any problems with engine knock on cold start?
Have spent heaps on new lifters, cam, timing chain etc.

It only knocks first in the morning, have had oil pressure tested that many times and all ok.
The oil and filter changed every 5,000 ks or sooner some times.

It has 195,300 on the clock, can not afford new motor.
Any help would be appreciated.

muggie

i was about to suggest,check out oil pump,what brand oil filter do you use? it may not have an anti drain back valve(unlikely though)as almost all modern day oil filter has this fitted,i'm more inclined to say it's piston slap,VN's are typically a noisy motor,but they shouldn't have the noise you are describing..when you first start it up does it sound like a diesel? if it does,it's definately piston slap.pistons are a technical thing ,i won't go into full detail,but when motor is cold,pistons are egg shaped,and as motor warms up,pistons expand to the round,some model cars..I.E the gemini were bad in their piston design,that the piston never really got out of the egg shape form,however VN's shouldn't do this,the design of their piston was good.

[muggie]

i was about to suggest,check out oil pump,what brand oil filter do you use? it may not have an anti drain back valve(unlikely though)as almost all modern day oil filter has this fitted,i'm more inclined to say it's piston slap,VN's are typically a noisy motor,but they shouldn't have the noise you are describing..when you first start it up does it sound like a diesel? if it does,it's definately piston slap.pistons are a technical thing ,i won't go into full detail,but when motor is cold,pistons are egg shaped,and as motor warms up,pistons expand to the round,some model cars..I.E the gemini were bad in their piston design,that the piston never really got out of the egg shape form,however VN's shouldn't do this,the design of their piston was good.

oil filter Ryco Z154 and Penrite oil

[s_pack]

s_pack cracked flywheel mabye??

Nah mate, saw it myself, was fine.

[Don Sutton]

Has anyone had any problems with engine knock on cold start?
Have spent heaps on new lifters, cam, timing chain etc.

It only knocks first in the morning, have had oil pressure tested that many times and all ok.
The oil and filter changed every 5,000 ks or sooner some times.

It has 195,300 on the clock, can not afford new motor.
Any help would be appreciated.

muggie

You most likely have piston slap, a problem usually associated with high k's but can be from near new such as the LS1 V8's. At that sort of k's it is a possibility. Some engines will go a lot longer before this develops. As engines are mass produced piston sizes are sorted for a best fit in the bore. If you get an engine on the high side of the tolerance range then piston slap will develop sooner than some one who has an engine on the bottom side. As soon as the piston heats up it expands to where the clearance reduces and the noise stops. Is this a problem?
Sometimes yes if it causes the knock sensor to think the engine is pinging (can happen when driving where the knock does not fully go though inaudible to the driver) and it retards the spark causing loss of performance.
There are occasions where the piston knock is more sinister in that the piston has actually cracked (this is not that common by the way) in which case it will eventually fail.
With a stethoscope (if you dont have one use a piece of plastic tube) you can listen to the block on each side to determine which bank is making the noise and see if it is detectable even with the engine warm. This will give a better idea on whether or not you need to do something. I don't know if the knock sensor will bring on the engine management light if it cant retard the spark far enough to avoid knocking on the Commodore (It does on the V6 Vectra as it did on mine with an 0.008" undersize piston). This would be a progression of the noise.

[hkmonaro68]

Another option is to add a little bit more oil, around 500ml more. VN-VP usually take after a sevice about 3.8ltrs of oil, VR-VS take 4.5, VT-VX 4.8. VY-VZ 6.2.
I think there is a lesson in those figs, every new model takes a bit more oil than the last.
Those figs are V6 engines only.
Ken

[samuels]

Another option is to add a little bit more oil, around 500ml more. VN-VP usually take after a sevice about 3.8ltrs of oil, VR-VS take 4.5, VT-VX 4.8. VY-VZ 6.2.
I think there is a lesson in those figs, every new model takes a bit more oil than the last.
Those figs are V6 engines only.
Ken

if you want to actually be technical the VN takes 4.1 litres with filter...3.8 without filter but yeah i can see what you mean by adding 500ml's+/-,assuming your'e talking with/without filter

[VPWAGZ]

yeah my v6 knocks on cold starts i get about 2 knocks then its normal, its also due for a service so i guess thats not helping

[Fu Manchu]

Mine does it and it is a brand spanking new motor! 2 or 3 seconds later all is quiet.
The old motor didn't do it?

[VTSSDUDE]

Thing is, where is the knocking sound coming from. Like my previous car a VN Commodore with 307,000km never made any cold noises, beautiful engine. But my Dad has a VR ute with 280,000 odd kms on it, and it knocks on cold startup.
Now lifters/rockers sound tinny, like shallow noises. Piston slap is a distant knocking sound or bottom end sounds similar. It's not normal, but engines that do have the knocking sound on cold startup seem to last just as long as engines that sound normal. Go figure, so this must mean as you are saying it has to be piston slap as I can't see this doing any major damage (providing you aren't revving the crap out of it while the knocking sound is present)
So conclusion to what I am saying is that for new/old engines that are making this sound there has to be play within the components of the engine somewhere, it's just a matter will or won't it cause any long term damage.
A lot of LS1 engines sound like tractors and still pull 12 second quarter miles and use no oil so if it happens to be piston slap then I wouldn't be to worried about it. Just a bit annoying hearing a knock in your engine on cold startup.

[iwishmyVNwouldstart]

i used to get really shithouse knocking coming from the heads, a rough idle, especially on a cold start, knock sensor came up on engine diagnosis, checked the knock sensor, oil all through it, ceaned it up, reset the computer, and she runs beautifully again, ill need to replace the sensor i think but soon.
if there is excessive piston slap, what needs to be done to fix it? i get a bit of bottom end noise form time to time too

[VTSSDUDE]

Excessive ring wear, worn gudgeon pins can cause piston slap, but if you aren't blowing any smoke then I would have to say the wear would have to be in your gudgeon pin where it slots into the piston. So not an easy job either way to fix. But is your knocking sound a deep knock or does it sound tinny?